Kicked spars for rudder and elevator applications

ABSTRACT

An aerodynamic structure incorporated in an aircraft control surface provides a spar extending along at least a portion of the control surface in a direction and the spar includes a plurality of bends along the direction of extension along the control surface to provide space to accommodate actuator fittings or other structural or operational requirements.

RELATED APPLICATIONS

This patent arises from a divisional of U.S. application Ser. No. 15/500,864, titled “Kicker Spars For Rudder And Elevator Applications,” filed Jan. 31, 2017, which is a § 371 national stage entry of PCT/US2014/058134, titled “Kicker Spars For Rudder And Elevator Applications,” filed Sep. 29, 2014, both of which are hereby incorporated by this reference in their entireties.

BACKGROUND INFORMATION Field

Embodiments of the disclosure relate generally to the field of structural systems for aircraft and more particularly to spars having offset webs to accommodate fittings or other structural limitations within low profile chord designs.

Background

Widespread use of composite structural systems with their associated high strength in aircraft has allowed tailoring of very thin cross-sections in aerodynamic surfaces with spars and other structure having reduced depth. However, in many cases, structural fittings, attachment limitations or other requirements are difficult to fit within the thin sections. In actuated surfaces with high loading, excessive moment arms may be required if fittings are placed in a standard structural arrangement within the thin sections. In addition it usually advantageous to locate the spar as close to the hinge line as possible. This creates challenges when attempting to locate fittings and maintain adequate space for joints.

It is therefore desirable to provide a structural design for spars used in such thin structures which allows more room to bolt the highly loaded actuator fittings or otherwise accommodate structural requirements without compromising the actuator fitting joint, compromising the repair capability, moving the spar within the design or otherwise aggravating hinge offsets and hinge loads, or segmenting the spar.

SUMMARY

Exemplary embodiments provide an aerodynamic structure incorporated in an aircraft aerodynamic control surface. A spar extends along the entire or at least a portion of the control surface in a direction and the spar includes a plurality of bends along spanwise direction of the control surface.

The embodiments disclosed provide a method wherein a determination is made of additional space requirements for actuator fittings or other structural or operational requirements. Chordwise offset of a spar kick corresponding to the additional space requirement is established and a profile for the web in the spar with appropriate inflection points, or break points, to accomplish the necessary kick is established.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of embodiments disclosed herein will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a side view of a rudder embodiment with the near side skin removed to expose the internal structure:

FIG. 2A is a pictorial view of the spar in the embodiment of FIG. 1 with angles exaggerated for clarity;

FIG. 2B is a side view of the spar with angles exaggerated for clarity;

FIG. 2C is a side detailed view of a first region of the spar showing a first “kick” with angles exaggerated for clarity;

FIG. 2D is a side detailed view of a second region of the spar showing a second kick with angles exaggerated for clarity;

FIG. 3 is a side view of the spar, ribs and fittings of the embodiment of FIG. 1;

FIG. 4A is a pictorial view of a first example rib and fitting adjacent an intermediate inflection point of the web in the first kick;

FIG. 4B is a side view of the first example rib and fitting;

FIG. 5A is a pictorial view of a second example rib and fitting adjacent an lower inflection point of the first kick;

FIG. 5B is a side view of the second example rib and fitting;

FIG. 6 is a flow chart of a method for implementation of the embodiment described herein;

FIG. 7 is is a flow diagram of aircraft production and service methodology in which the present embodiments may be employed; and,

FIG. 8 is a block diagram of an aircraft employing the embodiments.

DETAILED DESCRIPTION

For purposes of description herein, span refers to length of the aerodynamic control surface, chord refers to width of the control surface from a leading to a trailing edge and depth refers to the thickness of the control surface at a particular combination of span and chord. In description of placement of elements terms of spanwise or chordwise location may be employed. An exemplary embodiment of an aircraft control surface employs a spar composed of a conventional C-Channel which has a “kick” (bends) at several locations allowing the chordwise offset of the spar web to be optimized or alternatively, allows optimization of the chordwise placement of the spar along the entire span of the spar. The embodiments described herein may be specifically employed in rudder or elevator applications and will be described with respect to a rudder application. The rudder spar incorporates a web that bends in the forward and aft direction, relative to an installed orientation, or installation orientation, on an aircraft, at one or more spanwise locations to provide increased space at the areas of connection to actuators that control the movable rudder control surfaces. This structural arrangement allows the spar to be placed in the optimal position at each hinge or actuator fitting for the entire span of the spar.

Referring to the drawings, FIG. 1 shows a rudder 10 with the near side skin removed to show the underlying structure. The rudder 10 attaches to a vertical stabilizer on the aircraft on a hingeline 12. The structure of the rudder incorporates a plurality of ribs 14 a-14 f and a spar 16 which extends in a spanwise direction from a lower (inboard with respect to the span of the rudder) end plate 18 to an upper (spanwise outboard) cap structure 19. Skins 20 cover the rudder structure. The skins 20 may incorporate laminated build ups 22, 24 at rib locations and adjacent the spar. Fittings 26 a-26 l are employed for engaging hinge or actuator elements for operation of the rudder 10, as will be described in greater detail subsequently. Similar structure may be employed in an elevator employing the embodiment described.

Details of the spar 16 are shown in FIG. 2A. In the exemplary embodiment, due to the size requirements of actuators for the rudder 10, a standard linear web spar could not be used unless relocated aft from a forward edge 27 of the rudder to accommodate the actuator size, which would introduce longer fittings to accommodate the further spaced hingeline from the spar and the accompanying weight increase to accommodate structural requirements of such a configuration. The present embodiment incorporates a substantially “C” shaped spar having a top flange 28 and bottom flange 30 with a web 32 extending between the flanges. A first region 34 of the spar extends from a lower extent 36 to a first inflection point 38. At the inflection point 38, a first kick is provided in the spar and the web 32 is bent to angle aft extending for a first increment 40 to a second inflection point 42 wherein the web bends again to substantially parallel the hingeline for a second increment 44. At a third inflection point 46 the web bends to angle forward extending for a third increment 48 which terminates at a fourth inflection point 50. The first, second and third increments form a second region 52 of the spar. The aft relief of the second region 52 allows significant additional chordwise length in a connection region for mounting of actuator attachment fittings as will be described in greater detail subsequently. Upward in the drawing, outboard spanwise relative to the end plate, from the fourth inflection point the spar incorporates a third region 54 which again substantially parallels the hingeline. A second kick is provided in the exemplary embodiment commencing further outboard at a fifth inflection point 56 where the web 32 again angles aft for a fourth region 58 terminating at the connection to the cap structure.

The angular relationships of the 5 regions (angles have been exaggerated for clarity) can be seen in the side view of FIG. 2B substantially perpendicular to the flange 28 and parallel to the web 32.

The first kick, spar second region 52, is shown in detail in FIG. 2C. As best seen in FIG. 2C, the profile of flange 28 (and flange 30 hidden in the view of FIG. 2C) may be modified to provide additional chordwise length for structural enhancement or to provide coverage for fittings. For the embodiment shown, flange 28 is expanded, to establish an expanded profile, between the second the third inflection points 42, 46 forming the second increment 44 of the kick forming second region 52 with the expansion extending partially into the first and third increments 40, 48 proximate the second and third inflection points 42 and 46. Extended expansion areas 60 a, 60 b and 60 c at the locations of the fittings 26 d, 26 f and 26 h accommodate structural requirements for those fittings (shown in FIGS. 1 and 3). The spar can have any number of kicked regions to accommodate actuator, fitting or other hardware sizing designs while maintaining a desired overall chordwise length of the mating control surfaces.

The second kick, the spar fourth region 58, is shown in detail in FIG. 2D. As in the first kick, the flange 28 (and flange 30 hidden in the view of FIG. 2D) is expanded, to establish an expanded profile. However, the expansion covers the entire forth region 58 of the kick with the expansion extending partially into the third region 54 proximate the fourth inflection point 56. Expansion of the flange 28 over the forth region 58 as flange portion 62 provides additional structural capability for the upper end of the rudder 10 to accommodate the fittings 26 k and 26 l as well as the upper cap structure 19 (seen in FIGS. 1 and 3). Expansion of the flange 28, or flange 30, can occur at any location along the spar to accommodate actuator, fitting or other hardware sizing designs while maintaining a desired overall chordwise length of the mating control surfaces.

FIG. 3 demonstrates the interrelated locations of the spar 16, fittings 26 a-26 l and ribs 14 a-14 f in the rudder. Each of the ribs 14 a-14 f is placed adjacent an inflection point, or break point, in the spar web 32 bounding the regions of the spar providing the kicks. Fittings 26 b, 26 d, 26 f, 26 h, 26 j and 26 k are positioned to directly correspond with an associated one of the ribs. The combined rib and fitting attachment at adjacent the inflection points enhances the structural capability of the kicks in the spar. As seen in FIGS. 4A and 4B, as exemplary of the ribs in the third increment 44, rib 14 d provides support for the chord profile while employing a forward cap 64 to support the web 32 of the spar at the fourth inflection point 46. Fitting 26 h incorporates an aft surface 66 having a break angle corresponding to the web bend angle at the fourth inflection point 46 thereby supporting the web 32 at the inflection point by supporting the web between the aft surface 66 and forward cap 64 of the rib 14 d. As noted previously, the size and function of fitting 26 h and its associated interrelated components established the initial need for the kick, providing additional chordwise space for the actuator while maintaining the spar 16 closer to the hingeline coupling the rudder to the vertical tail. A similar configuration is present at rib 14 b with fitting 26 d at the second inflection point 42 initiating the third increment 44 of the spar forming the aft portion of the kick. Fittings 26 d and 26 h are longer in the chordwise direction than, for example, fitting 26 b, to position the fitting hinge through-hole at the hingeline. Similar structure incorporating the embodiment described may be employed in an elevator.

An interchangeable embodiment provides a fitting 26 a-26 k coupled to the web 32 without a rib 14 a-14 f sandwiching the web 32, or alternatively, a rib 14 a-14 f coupled to the web 32 without a fitting 26 a-26 k sandwiching the web 32, each of which by themselves structurally supports a bend in the spar 16.

Similarly as shown in FIGS. 5A and 5B, rib 14 a and fitting 26 b engage the web 32 at the first inflection point 38. Rib 14 a incorporates a forward angle plate 68 which engages the web 32 adjacent the inflection point and fitting 26 b includes an aft surface 70 having a break angle corresponding to the web bend angle at the first inflection point 38 thereby supporting the web 32 at the inflection point by sandwiching the web between the aft surface 70 and forward angle plate 68 of the rib 14 a. This configuration enhances the structure at the initiation of the kick at inflection point 38. A similar configuration is present at rib 14 e with fitting 26 j for the final inflection point of the first kick.

The embodiment disclosed for a kicked spar allows integration of fittings or other structural requirements that would otherwise require relocating of the spar or other structural modification. A method for implementation of a kicked spar is shown in FIG. 6 wherein a determination is made of additional chordwise length requirements for actuator fittings or other structural or operational requirements, step 602. A spar kick providing an offset corresponding to the additional chordwise length required is established, step 604 and a web profile with appropriate inflection points is established, step 606. Fittings and/or ribs are located adjacent the inflection points to support the kicked web profile, step 608, with the web supported between an aft surface of the fitting and a structural cap or plate on the rib. Flanges on the spar are expanded in the region of the kicked web, step 610, to establish an expanded profile for structural enhancement.

Examples of the disclosure may be described in the context of an aircraft manufacturing and service method 700 as shown in FIG. 7 and an aircraft 802 as shown in FIG. 8. During pre-production, exemplary method 700 may include specification and design 704 of the aircraft 702 and material procurement 706. During production, component and subassembly manufacturing 708 and system integration 710 of the aircraft 802 takes place. Thereafter, the aircraft 802 may go through certification and delivery 712 in order to be placed in service 714. While in service by a customer, the aircraft 802 is scheduled for routine maintenance and service 716 (which may also include modification, reconfiguration, refurbishment, and so on).

Each of the processes of method 700 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of venders, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.

As shown in FIG. 8, the aircraft 802 produced by exemplary method 700 may include an airframe 818 with a plurality of systems 820 and an interior 822. Examples of high-level systems 820 include one or more of a propulsion system 824, an electrical system 826, a hydraulic system 826, and an environmental system 830. Any number of other systems may be included.

Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method 700. For example, components or subassemblies corresponding to production process 708 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft 802 is in service. Also, one or more aspects of the apparatus, method, or a combination thereof may be utilized during the production stages 708 and 710, for example, by substantially expediting assembly of or reducing the cost of an aircraft 802. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft 802 is in service, for example and without limitation, to maintenance and service 716.

The examples described herein provide structure for aircraft control surfaces such as rudders and elevators. An aircraft 802 employing the embodiments provides enhanced operation by allowing the additional chordwise space for actuators or other requirements while maintaining the spar 16 closer to the hingeline coupling the control surface, the rudder or elevator in the described embodiments, to the associated vertical or horizontal stabilizer. In operation of the aircraft a hinge line actuator is actuated for movement of a control surface wherein the control surface incorporates a spar having a web with at least one kick bending at inflection points to provide a region having additional chordwise offset from a forward edge of the control surface to accomodate the hinge line actuator as defined for the presently described embodiments. The movement of the control surface is employed for aerodynamic control by inducing yaw or pitch for the described embodiments of a rudder or elevator.

Having now described various embodiments in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present disclosure as defined in the following claims. 

What is claimed is:
 1. A method for implementation of a kicked spar, the method comprising: determining additional chordwise length requirements; and establishing a spar kick having an offset corresponding to the additional chordwise length requirement and a web profile with appropriate inflection points.
 2. The method of claim 1, further including: locating fittings and associated ribs adjacent the inflection points to support the kicked web profile with the web.
 3. The method of claim 2, wherein locating fittings and associated ribs further includes supporting the web between an aft surface of the fitting and a structural cap or plate on the rib.
 4. The method of claim 2, further including: expanding flanges on the spar in the region of the kicked web for structural enhancement.
 5. A method for operating an aircraft, the method comprising: actuating a hinge line actuator for movement of a control surface, the control surface incorporating a spar having a web with at least one kick bending at inflection points to provide a region having additional chordwise offset from a forward edge of the control surface to accommodate the hinge line actuator; and employing the movement of the control surface for aerodynamic control.
 6. The method of claim 5, wherein the control surface is at least one of a rudder or an elevator and employing the movement includes inducing yaw or pitch for aerodynamic control. 